Bragg Creek
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bragg Creek clear sky chart from 2005-11-06 to 2024-03-01.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	8% 8% 4 7% 6% 4 5% 5% 6% 8% 38%	77932
	Night	5% 8% 4 7% 6% 4 5% 5% 6% 8% 41%	81429
Transparency	Day	41% 10% 15% 21% 11% 2	77640
	Night	38% 10% 15% 22% 12% 3	81301
Seeing	Day	13% 14% 30% 28% 12% 3	14283
	Night	10% 11% 34% 31% 12% 2	23596

By Month

Percentage Cloud Cover NW (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	1 5% 5% 11% 7% 5% 6% 5% 8% 9% 38%	2219
	11th to 20th	Day	1 6% 4 9% 7% 5% 7% 7% 8% 8% 39%	2299
	21st to end	Day	2 7% 3 7% 6% 4 5% 6% 6% 9% 44%	2794
February	1st to 10th	Day	2 7% 5% 8% 9% 5% 7% 7% 6% 9% 35%	1520
	11th to 20th	Day	1 7% 5% 9% 8% 5% 7% 7% 7% 9% 34%	1632
	21st to end	Day	1 9% 6% 12% 8% 4 7% 5% 6% 7% 34%	1555
March	1st to 10th	Day	2 8% 5% 8% 7% 5% 7% 6% 6% 7% 38%	1801
	11th to 20th	Day	3 8% 4 8% 7% 4 5% 5% 7% 9% 39%	1934
	21st to end	Day	5% 14% 7% 12% 7% 4 6% 6% 6% 8% 27%	2233
April	1st to 10th	Day	8% 14% 5% 8% 7% 5% 5% 5% 6% 8% 28%	2187
	11th to 20th	Day	10% 15% 6% 8% 6% 3 5% 4 6% 7% 30%	2310
	21st to end	Day	12% 14% 4 6% 6% 4 5% 5% 5% 7% 32%	2340
May	1st to 10th	Day	13% 13% 4 8% 8% 5% 6% 5% 5% 7% 27%	2453
	11th to 20th	Day	14% 9% 4 7% 6% 4 5% 5% 6% 8% 33%	2654
	21st to end	Day	22% 8% 3 6% 6% 4 5% 5% 5% 7% 27%	2917
June	1st to 10th	Day	19% 9% 3 7% 7% 4 6% 6% 7% 8% 27%	2700
	11th to 20th	Day	22% 9% 4 7% 6% 4 6% 5% 6% 7% 25%	2700
	21st to end	Day	10% 4 2 5% 5% 5% 7% 6% 8% 9% 38%	2700
July	1st to 10th	Day	10% 5% 2 6% 5% 4 6% 7% 7% 8% 40%	2700
	11th to 20th	Day	10% 5% 2 4 6% 4 5% 6% 7% 9% 44%	2700
	21st to end	Day	6% 3 2 4 4 3 5% 5% 7% 9% 51%	2837
August	1st to 10th	Day	11% 5% 2 5% 6% 3 5% 6% 7% 8% 43%	2507
	11th to 20th	Day	10% 4 2 4 4 3 5% 5% 6% 9% 49%	2345
	21st to end	Day	10% 5% 2 4 4 3 5% 5% 6% 8% 47%	2574
September	1st to 10th	Day	11% 6% 2 5% 5% 3 4 5% 5% 7% 48%	2217
	11th to 20th	Day	13% 7% 3 5% 5% 3 4 4 4 6% 46%	1985
	21st to end	Day	8% 8% 3 6% 4 3 4 5% 5% 9% 45%	1980
October	1st to 10th	Day	10% 10% 3 5% 5% 3 4 5% 6% 7% 41%	1924
	11th to 20th	Day	6% 10% 3 8% 6% 4 5% 4 6% 9% 40%	1640
	21st to end	Day	5% 10% 4 7% 6% 3 5% 6% 7% 8% 39%	1782
November	1st to 10th	Day	5% 12% 5% 8% 6% 3 6% 5% 6% 7% 37%	1584
	11th to 20th	Day	3 8% 4 6% 6% 5% 4 5% 6% 7% 45%	1425
	21st to end	Day	2 8% 6% 9% 7% 3 5% 5% 7% 7% 42%	1330
December	1st to 10th	Day	2 7% 5% 8% 8% 4 6% 4 8% 10% 38%	1330
	11th to 20th	Day	2 6% 4 11% 8% 5% 6% 6% 7% 10% 34%	1682
	21st to end	Day	3 8% 3 7% 6% 4 4 5% 6% 8% 47%	2442
January	1st to 10th	Night	1 9% 5% 9% 9% 6% 7% 7% 7% 9% 32%	4726
	11th to 20th	Night	1 6% 4 10% 9% 4 7% 7% 7% 8% 37%	4628
	21st to end	Night	2 8% 4 8% 8% 5% 6% 5% 6% 8% 40%	4862
February	1st to 10th	Night	3 7% 4 8% 7% 4 7% 6% 7% 10% 37%	2660
	11th to 20th	Night	3 10% 5% 8% 8% 4 6% 5% 5% 9% 37%	2434
	21st to end	Night	2 7% 5% 10% 9% 5% 6% 5% 5% 8% 39%	1897
March	1st to 10th	Night	1 7% 4 8% 8% 5% 6% 6% 8% 9% 36%	2165
	11th to 20th	Night	3 8% 3 6% 6% 3 6% 6% 6% 11% 41%	2025
	21st to end	Night	4 11% 5% 10% 6% 4 6% 6% 6% 9% 34%	2120
April	1st to 10th	Night	5% 13% 6% 8% 7% 2 4 5% 7% 8% 34%	1772
	11th to 20th	Night	8% 13% 6% 9% 6% 3 3 4 6% 8% 34%	1601
	21st to end	Night	7% 14% 3 7% 5% 3 4 4 6% 9% 37%	1620
May	1st to 10th	Night	11% 13% 4 7% 4 4 5% 5% 5% 9% 33%	1504
	11th to 20th	Night	11% 8% 3 5% 6% 2 4 4 5% 10% 42%	1239
	21st to end	Night	19% 9% 3 6% 4 3 4 5% 5% 7% 34%	1358
June	1st to 10th	Night	16% 7% 3 5% 5% 3 6% 6% 6% 8% 35%	1260
	11th to 20th	Night	20% 8% 2 5% 5% 4 4 5% 6% 8% 33%	1260
	21st to end	Night	8% 3 2 4 5% 3 5% 6% 7% 10% 47%	1260
July	1st to 10th	Night	8% 5% 2 3 4 3 5% 4 7% 9% 50%	1260
	11th to 20th	Night	7% 6% 2 5% 4 3 5% 5% 6% 8% 49%	1260
	21st to end	Night	6% 4 1 4 2 2 5% 4 5% 7% 59%	1477
August	1st to 10th	Night	11% 5% 2 4 4 2 3 4 7% 8% 52%	1432
	11th to 20th	Night	10% 3 1 3 3 2 4 5% 7% 9% 53%	1554
	21st to end	Night	10% 4 2 3 3 2 3 4 6% 7% 55%	1782
September	1st to 10th	Night	11% 7% 2 3 4 3 4 3 6% 8% 50%	1741
	11th to 20th	Night	14% 8% 1 4 3 2 3 4 5% 6% 49%	1975
	21st to end	Night	9% 8% 2 4 4 2 4 4 6% 8% 50%	1980
October	1st to 10th	Night	10% 9% 3 5% 5% 3 5% 5% 5% 7% 44%	2035
	11th to 20th	Night	7% 8% 3 5% 5% 3 3 5% 7% 9% 45%	2317
	21st to end	Night	5% 8% 4 8% 5% 4 5% 6% 6% 8% 42%	2574
November	1st to 10th	Night	4 12% 5% 7% 6% 3 5% 6% 6% 7% 39%	2476
	11th to 20th	Night	3 7% 3 7% 6% 4 5% 5% 6% 8% 46%	2751
	21st to end	Night	2 8% 5% 8% 7% 4 5% 6% 6% 9% 42%	2850
December	1st to 10th	Night	3 8% 4 8% 7% 4 6% 5% 7% 10% 37%	2850
	11th to 20th	Night	1 7% 4 9% 8% 4 6% 7% 8% 8% 37%	3510
	21st to end	Night	2 7% 4 7% 6% 4 6% 7% 6% 7% 45%	5214

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	37% 9% 15% 25% 11% 3	2219
	11th to 20th	Day	39% 9% 10% 19% 20% 4	2320
	21st to end	Day	32% 12% 16% 29% 9% 1	2794
February	1st to 10th	Day	42% 13% 13% 19% 10% 4	1520
	11th to 20th	Day	42% 10% 16% 19% 10% 2	1641
	21st to end	Day	47% 9% 14% 16% 13% 1	1555
March	1st to 10th	Day	43% 10% 17% 19% 10% 1	1801
	11th to 20th	Day	39% 9% 15% 23% 11% 2	1935
	21st to end	Day	54% 10% 15% 15% 6% 1	2233
April	1st to 10th	Day	50% 10% 16% 15% 8% 1	2187
	11th to 20th	Day	53% 7% 13% 17% 9% 1	2310
	21st to end	Day	50% 9% 14% 19% 7% 1	2340
May	1st to 10th	Day	54% 8% 15% 16% 6%	2453
	11th to 20th	Day	46% 10% 13% 21% 9% 1	2658
	21st to end	Day	54% 9% 16% 16% 6%	2918
June	1st to 10th	Day	53% 10% 15% 13% 8% 1	2700
	11th to 20th	Day	57% 8% 14% 13% 7% 1	2700
	21st to end	Day	38% 12% 18% 21% 9% 2	2700
July	1st to 10th	Day	37% 11% 17% 21% 11% 2	2626
	11th to 20th	Day	35% 11% 15% 24% 13% 2	2619
	21st to end	Day	27% 10% 16% 30% 16% 2	2679
August	1st to 10th	Day	36% 11% 16% 25% 11% 2	2490
	11th to 20th	Day	32% 8% 21% 28% 10% 2	2345
	21st to end	Day	32% 10% 15% 28% 13% 2	2574
September	1st to 10th	Day	35% 8% 16% 24% 15% 3	2217
	11th to 20th	Day	38% 7% 15% 24% 14% 2	1985
	21st to end	Day	36% 9% 16% 25% 12% 2	1980
October	1st to 10th	Day	42% 9% 14% 23% 11% 2	1924
	11th to 20th	Day	39% 9% 17% 22% 11% 3	1640
	21st to end	Day	40% 10% 14% 20% 14% 2	1782
November	1st to 10th	Day	44% 10% 13% 19% 12% 1	1584
	11th to 20th	Day	35% 10% 17% 25% 12% 2	1425
	21st to end	Day	38% 9% 18% 22% 10% 4	1330
December	1st to 10th	Day	39% 10% 16% 18% 13% 4	1330
	11th to 20th	Day	39% 14% 16% 19% 10% 1	1684
	21st to end	Day	33% 8% 10% 25% 19% 5%	2442
January	1st to 10th	Night	41% 13% 15% 20% 8% 2	4726
	11th to 20th	Night	40% 10% 12% 16% 15% 6%	4669
	21st to end	Night	36% 13% 15% 22% 13% 1	4862
February	1st to 10th	Night	40% 12% 12% 20% 13% 3	2660
	11th to 20th	Night	43% 9% 16% 18% 13% 2	2435
	21st to end	Night	43% 7% 11% 21% 14% 3	1897
March	1st to 10th	Night	40% 11% 16% 22% 8% 2	2165
	11th to 20th	Night	35% 11% 16% 23% 14% 1	2025
	21st to end	Night	44% 11% 15% 19% 10% 1	2120
April	1st to 10th	Night	45% 9% 14% 20% 11% 1	1772
	11th to 20th	Night	49% 7% 12% 21% 9% 1	1601
	21st to end	Night	44% 9% 15% 21% 8% 2	1620
May	1st to 10th	Night	46% 8% 15% 20% 10% 1	1504
	11th to 20th	Night	38% 7% 16% 28% 9% 1	1239
	21st to end	Night	48% 9% 15% 21% 6% 1	1358
June	1st to 10th	Night	45% 8% 17% 21% 8%	1260
	11th to 20th	Night	47% 7% 17% 18% 8% 2	1260
	21st to end	Night	31% 10% 20% 27% 10% 2	1260
July	1st to 10th	Night	28% 11% 20% 25% 14% 1	1225
	11th to 20th	Night	32% 8% 17% 28% 12% 2	1218
	21st to end	Night	23% 8% 16% 32% 19% 3	1395
August	1st to 10th	Night	29% 10% 16% 31% 11% 2	1424
	11th to 20th	Night	25% 9% 20% 33% 12% 1	1554
	21st to end	Night	25% 8% 16% 31% 17% 3	1782
September	1st to 10th	Night	32% 7% 16% 27% 15% 2	1741
	11th to 20th	Night	34% 6% 16% 26% 13% 4	1975
	21st to end	Night	31% 8% 17% 26% 14% 4	1980
October	1st to 10th	Night	38% 9% 13% 24% 14% 2	2035
	11th to 20th	Night	34% 8% 19% 24% 12% 3	2317
	21st to end	Night	38% 10% 16% 23% 12% 1	2574
November	1st to 10th	Night	43% 8% 14% 20% 13% 2	2476
	11th to 20th	Night	35% 9% 15% 22% 17% 2	2751
	21st to end	Night	37% 9% 17% 21% 12% 4	2850
December	1st to 10th	Night	40% 10% 14% 21% 11% 4	2850
	11th to 20th	Night	37% 16% 17% 21% 8% 1	3507
	21st to end	Night	34% 10% 13% 22% 15% 6%	5214

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	3 12% 32% 31% 14% 7%	180
	11th to 20th	Day	7% 9% 37% 33% 12% 2	180
	21st to end	Day	8% 15% 33% 31% 11% 3	198
February	1st to 10th	Day	9% 20% 34% 23% 8% 5%	180
	11th to 20th	Day	5% 15% 35% 35% 9% 1	255
	21st to end	Day	4 23% 29% 34% 10% 1	367
March	1st to 10th	Day	8% 19% 40% 22% 9% 2	421
	11th to 20th	Day	7% 20% 36% 25% 8% 3	420
	21st to end	Day	12% 24% 31% 21% 9% 2	462
April	1st to 10th	Day	13% 21% 35% 24% 6% 1	420
	11th to 20th	Day	19% 17% 29% 23% 10% 2	412
	21st to end	Day	19% 21% 26% 21% 10% 2	420
May	1st to 10th	Day	21% 16% 24% 25% 10% 4	429
	11th to 20th	Day	19% 12% 22% 27% 16% 4	625
	21st to end	Day	22% 8% 22% 27% 18% 3	679
June	1st to 10th	Day	19% 12% 30% 27% 10% 2	630
	11th to 20th	Day	23% 13% 27% 24% 10% 2	630
	21st to end	Day	11% 10% 27% 31% 16% 4	630
July	1st to 10th	Day	13% 6% 24% 34% 18% 4	621
	11th to 20th	Day	11% 10% 28% 30% 17% 3	618
	21st to end	Day	6% 8% 31% 34% 15% 5%	583
August	1st to 10th	Day	12% 7% 29% 33% 13% 5%	447
	11th to 20th	Day	11% 7% 29% 35% 13% 5%	437
	21st to end	Day	12% 14% 26% 31% 12% 5%	495
September	1st to 10th	Day	15% 13% 31% 26% 11% 3	450
	11th to 20th	Day	18% 11% 26% 29% 14% 2	450
	21st to end	Day	17% 19% 29% 24% 9% 3	450
October	1st to 10th	Day	14% 13% 31% 25% 14% 3	394
	11th to 20th	Day	13% 15% 31% 27% 11% 3	270
	21st to end	Day	14% 20% 34% 22% 7% 2	297
November	1st to 10th	Day	16% 17% 37% 22% 6% 1	270
	11th to 20th	Day	12% 15% 39% 25% 8% 1	225
	21st to end	Day	8% 17% 37% 22% 9% 8%	180
December	1st to 10th	Day	4 12% 43% 26% 11% 4	180
	11th to 20th	Day	4 16% 35% 35% 7% 3	180
	21st to end	Day	6% 10% 31% 37% 13% 4	198
January	1st to 10th	Night	8% 15% 42% 27% 7% 1	950
	11th to 20th	Night	6% 13% 44% 28% 7% 1	905
	21st to end	Night	7% 16% 42% 26% 8% 1	836
February	1st to 10th	Night	5% 17% 37% 26% 12% 3	760
	11th to 20th	Night	7% 13% 36% 31% 11% 1	744
	21st to end	Night	6% 9% 39% 27% 17% 3	628
March	1st to 10th	Night	5% 11% 42% 29% 11% 3	722
	11th to 20th	Night	7% 12% 39% 29% 11% 2	720
	21st to end	Night	9% 11% 32% 34% 11% 3	792
April	1st to 10th	Night	11% 11% 32% 34% 10% 2	692
	11th to 20th	Night	17% 11% 34% 29% 10%	533
	21st to end	Night	14% 11% 31% 30% 12% 1	540
May	1st to 10th	Night	17% 10% 25% 31% 16% 1	432
	11th to 20th	Night	16% 5% 25% 34% 19% 1	354
	21st to end	Night	21% 5% 22% 31% 20% 1	389
June	1st to 10th	Night	19% 7% 24% 36% 13% 1	360
	11th to 20th	Night	21% 5% 29% 29% 14% 1	360
	21st to end	Night	11% 4 23% 35% 25% 2	360
July	1st to 10th	Night	13% 3 18% 41% 24% 1	350
	11th to 20th	Night	9% 4 24% 43% 19% 2	348
	21st to end	Night	6% 5% 17% 44% 25% 2	394
August	1st to 10th	Night	14% 2 14% 38% 28% 3	358
	11th to 20th	Night	10% 3 19% 41% 24% 3	486
	21st to end	Night	11% 6% 21% 41% 20% 2	594
September	1st to 10th	Night	14% 4 26% 33% 18% 5%	661
	11th to 20th	Night	18% 5% 19% 34% 19% 5%	720
	21st to end	Night	13% 8% 33% 30% 11% 4	720
October	1st to 10th	Night	14% 8% 29% 33% 14% 3	720
	11th to 20th	Night	11% 10% 34% 30% 13% 2	720
	21st to end	Night	7% 15% 38% 31% 8% 1	792
November	1st to 10th	Night	12% 12% 43% 24% 8% 1	811
	11th to 20th	Night	9% 17% 44% 25% 4 1	950
	21st to end	Night	6% 14% 46% 24% 8% 2	950
December	1st to 10th	Night	7% 15% 40% 27% 9% 2	950
	11th to 20th	Night	4 13% 44% 30% 7% 1	950
	21st to end	Night	7% 12% 40% 30% 9% 2	1045

Page generated at 2024-02-27 04:30:13. Version ac07

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